An impedance CT system utilizes the fact that media have individual electric impedance values, to find spatial media distributions in a three-dimensional object. The impedance CT system passes a current through an object, measures a potential distribution induced at the surface of the object, and visualizes an impedance distribution in the object according to the potential distribution. The system is applicable to measuring the distributions of blood, lungs, fat, etc., in a human body (“BME” Vol. 8, No. 8 (1994), p. 49, Japanese Society for Medical and Biological Engineering).
In addition to the impedance CT system, there are other apparatuses that measure electric impedance values and find subcutaneous and visceral fat quantities. An example of such apparatuses is “Body Fat Measuring Apparatus” disclosed in Japanese Patent Laid Open Publication No. 11-113870 (first prior art). Another example is “Internal Fat Measuring Instrument” disclosed in Japanese Patent Laid Open Publication No. 11-123182 (second prior art). The first prior art attaches a plurality of electrodes to the surface of a body, measures impedance values between the electrodes, and creates an impedance matrix for a cross section of the body. Thereafter, an operation unit calculates the product of the impedance matrix and a coefficient matrix prepared from information on the electrode attached parts of the body entered through an input unit, and provides a cross-sectional body fat distribution. The second prior art winds a belt around the body of a subject. The inner side of the belt is provided with electrode pairs each consisting of a current path forming electrode and measuring electrode. The electrode pairs are arranged substantially at regular intervals. Two electrode pairs are chosen, and an AC current is passed between the current path forming electrodes of the chosen electrode pairs, to form a current path. The measuring electrodes measure an impedance value in the current path. The two electrode pairs are properly chosen so that adjacent electrodes may mainly measure subcutaneous fat and opposing electrodes may mainly measure visceral fat.